Many Hawaii residents have heard the legend that it's bad luck to take lava rocks from Kilauea volcano. That's probably something a Hawaiian Airlines flight attendant was thinking when she spotted a child with a lava rock sticking out of his backpack Wednesday morning at Kahului Airport.

In a Facebook post that's gone viral, the flight attendant asked the boy where he had gotten the rock. He replied that it was from the Big Island and that it was being taken home as a souvenir.

She explained to the boy why he shouldn't take it home with him. And a few minutes later, the boy and his family returned several large lava rocks and two bags and black sand that they had in their carry-on bags.

"O.M.G. What is she going to do with all this stuff?" asked Hawaiian cultural practitioner Vicky Holt Takamine of the Pa`i Foundation, when she was shown a photo of the rocks and sand.

"I have no idea what they're going to do with all of this," she said. "What are they going to do? Are they building an 'ahu (altar)? or are they just going to make a little sand pile in the back of their yard and say, 'We went to Hawaii and here's our little corner'?"

The box was taken back to Hilo, and the rocks and sand returned. A follow-up video was posted showing the return of the materials.

"If you're planning on coming to Hawaii, you do not take no rocks, you don't take no sand back home, 'cause it's bad luck," says a man in the video, holding the box with the rocks and sand.

"It's true! The goddess Pele, especially on Hawaii island," said Takamine. "Well, all of these islands. These islands have been formed by the goddess Pele."

It's also illegal to take rocks and minerals from any national park. Taking such things as black sand and lava rock depletes a geological resource -- another reason to leave the rocks undisturbed.

Even if the rocks and sand did not come from Hawaii Volcanoes National Park, the state Department of Land and Natural Resources said it is also illegal to take sand and rock from any public beach.

Whether or not you believe the legend, Volcanoes National Park does get a lot of rocks returned to it from people, with many saying they've experienced bad luck.

"The tourists need to understand you don't just come in, take what you want and leave," said Takamine. "Because it may come back to bite you."